The power semiconductor devices of power systems are typically integrated to form a power module. Most power modules thus include power semiconductor devices, such as power diodes and power MOSFETs. A power semiconductor device generates heat during operation. The heat so generated affects the operation of the semiconductor device, and also may have an adverse effect on the structural integrity of the power module by for example creating thermal stresses which may lead to fractures and other mechanical damage. The heat generated by the power semiconductor devices must, therefore, be extracted and dissipated. Otherwise the continued operation of the power semiconductor devices may be jeopardized.
In a conventional power module, the generated heat is typically passed to a heatsink for dissipation. Serving as a thermal conduit is usually a thermally conductive substrate which is interposed between the heat generating power semiconductor devices and the heatsink.
A known thermally conductive substrate is referred to as insulated metal substrate (IMS). Another known thermally conductive substrate is direct bonded copper (DBC). The use of an IMS or a DBC is undesirable due to cost, increase in the thermal resistance of the entire stack in the application, thermal capacitance at the die, and typically higher electrical loop resistance of the power module. Due to the less than ideal heat extractive capabilities of a design that includes and IMS or a DBC, the reaching of the maximum rating of a power semiconductor device is avoided to prevent overheating. Thus, the use of an IMS or a DBC may hinder the designers to take full advantage of the capability of a power semiconductor device, which may lead to inefficient power designs, among other disadvantageous results.
Power modules are prevalently used in the automotive industry, particularly for the driving and the control of electric motors, among other uses. The increase in the number of features in an average automobile has caused and continues to cause an increased demand for generic or function-specific power modules. Yet, the market place demands reduction of cost per module as well as module efficiency so that the final cost of the car remains competitive and electric power used by the extra features requires as little extra power demand as possible on the automobile's electric system.
Thus, it is desirable to have a power module which can adequately dissipate the generated heat without using a thermally conductive substrate.